This invention relates generally to a magnetic recording medium and more particularly to a magnetic recording medium allowing high density recording by enlargement of the magnetic moment in the direction perpendicular to the surface of the magnetic recording medium. When the recorded magnetic moment is increased in the direction of the medium thickness, that is, in the direction perpendicular to the medium surface, recording density on a magnetic recording medium can be increased. When recording density is increased still more, magnetization on the medium is primarily with moments in the perpendicular direction. Accordingly, it is advisable to apply a magnetic field in the direction which is perpendicular with respect to the medium surface in advance of recording. Further, with regard to the recorded magnetization on the medium, it is also advisable to provide a medium whereon the magnetic moments are oriented in advance in the direction perpendicular to the surface. Generally, perpendicular magnetic recording is a technique to record and reproduce in the direction of thickness of the medium, that is, in the direction perpendicular to the medium surface. That is described in detail in The Journal of Magnetics Society of Japan, "Possibilities of Perpendicular Magnetic Recording" , May 26, 1977.
In prior art perpendicular magnetic recording, the medium is recorded in the perpendicular direction. However, in these recording systems, recorded magnetization is generally decreased through a diamagnetic field produced by the medium itself. Also, the magnetic field at the edge portion of the magnetic head has a relatively large component which is parallel to the medium surface. Accordingly, when information is recorded magnetically by moving the medium relatively against the magnetic pole, the medium is magnetized by the magnetic field at the trailing edge portion of the pole relative to the moving direction of the head. Consequently, parallel components of the recording magnetic field primarily form the magnetic moments stored in the medium. This phenomenon is unfavorable for perpendicular magnetic recording and reproduction. Further, quality of recording and reproduction is adversely affected when the recording medium itself does not have its crystals magnetically oriented perpendicular to the medium surface.
What is needed is a magnetic recording medium having a recording surface with favorably oriented crystal structure and a construction which lends itself to perpendicular magnetization without substantial parallel magnetic components.